Speaking at Oxford last fall, one of the topics Tim Cook talked about was purpose:
I have begun to think through... What is my purpose in life? I was struggling with a lot of things both professionally and personally at that time. And it began to dawn on me then that the purpose of life wasn’t to love your job. It was to serve humanity in a broad way. The outcome of doing that would mean that you would love your job.
You can find the video here.